CONCENTRIC CO-EXTRUSION DIE AND A METHOD OF EXTRUDING A MULTILAYER THERMOPLASTIC FILM

摘要

A large concentric co-extrusion die (1) is described having a plurality of annular or conical die mandrel layers (201-205). Each layer is formed between a pair of adjacent annular or conical die mandrels (101-106) defining between them a flow path for molten thermoplastics material from an inlet to an annular extrusion outlet (110) through which a thermoplastics tubular extrusion is formed in use. Extrusion takes place through the multiple annular layer outlets (301-305) to form a multi-layered product. At least one layer (203) of the annular or conical die mandrels has a plurality of molten material inlets arranged around the external circumference of the co-extrusion die with each inlet being connected to a feed channel (403) which has plural bifurcations (403.1, 403.2, 403.3) providing 2n subsidiary outlet feed channels (503) where n is the number of bifurcations. Each subsidiary outlet feed channel being connected to a corresponding helical outlet channel (703).

主权项

1. A concentric co-extrusion die comprising:
an annular extrusion outlet having a diameter equal to or greater than 1300 mm and having a plurality of die mandrel layers having a pair of adjacent annular or conical die mandrels defining between them a flow path for molten thermoplastics material; and an inlet to the annular extrusion outlet through which a thermoplastics tubular extrusion is formed in use, wherein at least one of said layers has a plurality of molten material inlets arranged spaced apart around an external circumference of a co-extrusion die, each molten material inlet being connected to a feed channel which has a plurality of bifurcations providing 2n subsidiary outlet feed channels with n being the number of bifurcations, each subsidiary outlet feed channel being connected to a corresponding helical outlet channel, and wherein extruding the molten material through the at least one of said layers forms a multi-layered product.